The electrician I have coming to finally upgrade my service entrance and main panel is unavailable for a couple of days, and I need to go get some wire (tomorrow) before I can talk with him again. He does not take credit cards and I only have enough cash for his labor and miscellaneous parts, and that is why I am the one buying the wire ...

... and I forgot to ask him specifically what he needs for the run to my wife's washer/dryer combo unit.

The unit needs 240V (30A), but I do not know whether to get 10-2 w/G, 10-3 or 10-3 w/G. I will be getting some regular 10-2 w/G for a water heater to be installed later on, but the washer/dryer combo has 120V stuff internally and that makes me think I should have either 10-3 and then run an equipment ground to a pipe or else use 10-3 w/G so there is a regular "shared neutral" for the 120V aspects of the combo unit either way. So, which should I buy tomorrow:

10-2 w/G, 10-3 or 10-3 w/G?

The unit is presently running on 12-3 (a pre-existing dryer line based on an ancient code allowing 30A on 12ga wire, I assume, and we never run the washer and dryer at the same time (and the dryer only draws 20A)), and then the unit also has a separate ground wire running from chassis to a nearby copper pipe, but I will get 10-3 w/G if that is what the inspector will be expecting to see.

I thank you! I have yet to see the new 4-prong plug and receptacle, but I will get those today also. When my wife and I got the combo unit several months ago, I used the pigtail from the old dryer and then added the equipment ground.

I thank you! I have yet to see the new 4-prong plug and receptacle, but I will get those today also. When my wife and I got the combo unit several months ago, I used the pigtail from the old dryer and then added the equipment ground.

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What you added was not an equipment ground. The equipment ground MUST land on the grounding terminal bar in the panel. All you did was install a wire from the unit to the pipe that served no purpose at all.

What you added was not an equipment ground. The equipment ground MUST land on the grounding terminal bar in the panel. All you did was install a wire from the unit to the pipe that served no purpose at all.

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If that is True then why does the Manufacture tell you to connect it that way ?

The "grounding terminal on the bar IS bonded/connected to the unit's "body", otherwise IT would "serve no purpose", so a ground wire from ANYWHERE on the frame to a continuous metal water line WOULD serve its intended purpose.

If that is True then why does the Manufacture tell you to connect it that way ?

It is better than no Ground at all, And Does serve its purpose.

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The NEC nor any Nationally Recognized Testing Lab allows the connection from the frame of an appliance to a metal water pipe as a path for fault current.

How effective would this be should the piping system have any type of nonmetallic pipe installed? None, it would serve no purpose at all.
The nice thing about this site is one can address repairs to metal water pipes with non-metallic piping parts and get the answer in just a few seconds. There is no requirement in the plumbing code to replace metal with metal.

Then we have 300.3 of the NEC
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

This Section does not allow the EGC to be installed from a frame to a pipe

It might not meet code, but it would seem that if the copper piping system in the house is bonded to the panel, (as most are) it would accomplish the same thing as a separate equipment ground. I don't think the electrons will care one way or the other.

I'm no endorsing it, but to say that it "served no purpose at all" sounds like a false statement to me.

It might not meet code, but it would seem that if the copper piping system in the house is bonded to the panel, (as most are) it would accomplish the same thing as a separate equipment ground. I don't think the electrons will care one way or the other.

I'm no endorsing it, but to say that it "served no purpose at all" sounds like a false statement to me.

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Now address the repair using a nonmetallic part, please. Would those electrons have a path to travel? Therefore the statement that I stand by, it serves no purpose at all

Edited to add;
If you can ensure that the metal water pipe will never be repaired in the future with nonmetallic parts then you might have a leg to stand on but I don’t know anyone who will live forever or even past the expected use of the building therefore the connection from the frame to the pipe is useless.

It was not uncommon in the past for dryers/ranges to be connected to a THREE prong 125/250 receptacle. The WHITE, NEUTRAL wire was connected to the metal chassis. This was considered an "acceptable compromise" and the dryer instructions may indeed still suggest connecting a ground wire to a water pipe.
a) The electrical code was changed probably 20 years? ago to not allow the 3 prong connection.
b) At the time, there was NOTHING but copper or galvanized that had ever been allowed as water pipe ( well, lead and brass also) so the issue with plastic pipe was still a figment of someones imagination.
c) There are documented incidents of shock to homeowners or plumbers when a meter or other inline connection was removed only to find that the household water pipe was energized. Hence, if instruction still suggest a "ground wire" , such is NOT good advice. Instructions also say to comply with all codes, and that is the final word;

What you added was not an equipment ground. The equipment ground MUST land on the grounding terminal bar in the panel.

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Following my other thread where I learned how very little current can actually be carried away by a ground rod, no argument here, and "equipment ground" was merely a convenient term I used when mentioning the "ground wire" suggested by the manufacturer.

Unrelated story: Back in the '60s, I once got caught in the current flowing between a large drill with a metal case and a gas line I had grabbed for support while standing on a ladder to drill a hole up through the floor, so that house certainly had an effective ground of some kind in its plumbing!

Following my other thread where I learned how very little current can actually be carried away by a ground rod, no argument here, and "equipment ground" was merely a convenient term I used when mentioning the "ground wire" suggested by the manufacturer.

Unrelated story: Back in the '60s, I once got caught in the current flowing between a large drill with a metal case and a gas line I had grabbed for support while standing on a ladder to drill a hole up through the floor, so that house certainly had an effective ground of some kind in its plumbing!

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Was it in the plumbing or the gas line?

If there is a three wire receptacle with the frame of the appliance bonded to the neutral and a conductor from the frame to a bonded metal water pipe then what has happened is the metal water pipe is just energized and should a plumber have to repair the metal water pipe we have just put him in danger.

If there is a three wire receptacle with the frame of the appliance bonded to the neutral and a conductor from the frame to a bonded metal water pipe then what has happened is the metal water pipe is just energized and should a plumber have to repair the metal water pipe we have just put him in danger.

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That was a long time ago, but the pipe was black so I assume it was a gas line installed by a plumber (and maybe an electrician later added some kind of "ground" wire), and yes, I understand the danger you have described. So, I am now a firm believer in having a *true* equipment ground all the way back to the panel!

quote; then what has happened is the metal water pipe is just energized and should a plumber have to repair the metal water pipe we have just put him in danger.

That would only occur if there were an additional problem in the system, such as a failed neutral in the utility's feed. Then, the piping would function as the neutral UNTIL the plumber "broke" the continuity. I had it happen many times years ago. In Chicago, when we separated a water line, we NEVER used our hands. We hit the pipe with a wrench to see if there was a spark between the two pieces. One time, everything in the house that was turned on burned out when I disconnected the water line to the water heater. I have also been walking through a house, or in one case UP TO THE TRAILER, when my TicTracer went off indicating that some metal object was energized. Usually, the occupants did not know of the hazard because they could not touch the object and a "ground source" at the same time.

That would only occur if there were an additional problem in the system, such as a failed neutral in the utility's feed.

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If the piping was metal to the point of entry and there was nonmetallic underground supplying the building then the open neutral somewhere else would not affect the metal pipes in the building, but, the bond to the metal pipe from an appliance if the metal pipe was bonded to the service as required by 250.104 there would be a parallel path between the neutral of the appliance and the water pipe.

Should the metal water pipe be broke then the two sections would be at different potentials and a shock hazard would be present for anyone touching the two pieces of pipe.
One path from the appliance frame that has a three wire connection, on the neutral to the service. The second parallel path from the appliance through the bonding jumper to the metal pipe down the metal pipe to the required bonding to the service.

Getting between the water pipe would be the same thing as getting between the neutral conductor as both are a parallel path from the appliance back to the service equipment.